Intensity-dependent topographical expansion of sensory representations.

Area of Science:

• Neuroscience
• Sensory Perception
• Brain Imaging

Background:

• Traditional neuroimaging assumes fixed neural populations encode sensory properties via response magnitude.
• This overlooks the role of activation topography's spatial extent, despite its behavioral relevance.
• Stimulus intensity is a fundamental sensory property varying across modalities, making it ideal for studying topographical coding.

Purpose of the Study:

• To investigate if higher stimulus intensity correlates with expanded activation topography.
• To determine if this phenomenon is consistent across different sensory modalities and datasets.
• To challenge the prevailing assumption of fixed neural topography in sensory coding.

Main Methods:

• Utilized a Bayes factor-based approach with four functional magnetic resonance imaging (fMRI) datasets (N=609 total, plus a precision dataset).
• Administered sensory stimuli (somatosensory, auditory, visual) at varying intensities.
• Analyzed changes in activation topography in response to stimulus intensity variations.

Main Results:

• High-intensity stimulation consistently induced topographical expansion in somatosensory, visual, and cerebellar regions.
• This expansion was replicated across large-scale and precision datasets, and within individual participants.
• Topographical expansion was also observed for tactile, auditory, and visual stimuli, correlating with discriminability.

Conclusions:

• Topographical expansion is a robust and replicable feature of intensity coding across multiple sensory modalities.
• Findings challenge the long-held assumption of fixed neural topography in sensory processing.
• Activation topography's spatial dynamics are crucial for encoding stimulus intensity and potentially other sensory features.